<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <link rel="stylesheet" href="./index.css">
    <title>返回页面顶部</title>
</head>
<body>
    <div style="height: 2000px;"></div>
    <button id=btn>click</button>

    <!-- <script src="./test.js"></script> -->
    <script src="./index.js"></script>
</body>
</html>